The invention relates to sorbic acid and its derivative potassium sorbate for use as a preventative against rust, corrosion and scale that usually forms on metal surfaces.
Sorbic acid and its salts are commonly used to preserve foods such as cheese, fish, meat, vegetables, fruit, non-alcoholic beverages, wine, confectioneries and baked goods. Sorbic acid and its salts are also used as preservatives in some pharmaceuticals and cosmetics. Potassium sorbate (hereinafter PS) or 2,4 hexadienoic acid potassium salt, is extensively used as a wide spectrum anti-microbial for maintaining freshness in foods, beverages, animal feed, cosmetics and as a preservative for products destined to come in contact with foodstuffs such as adhesives for food packaging. PS has excellent water solubility as compared to sorbic acid which has low water solubility. PS is highly effective against most micro-organisms, is economical and has obtained worldwide approval for use in a wide variety of foods. The concentration of sorbic acid and its salts as a preservative, in food in which the preservative is evenly dispersed, is about 0.1% and generally falls in the range of 0.05% to 0.3%. Some food products are dipped or sprayed with a PS solution that has a concentration of 5-10%, however, the concentration of the preservative in these final products fall within the above range.
The effectiveness of all food preservatives is highly dependent upon the pH of the preservative. The optimum effectiveness of PS as a food preservative is when it is used below pH 6.0. However, it is an effective food preservative at up to pH 6.5 which qualifies PS to be used in a very wide variety of foods.
The major manufacturer of potassium sorbate in the United States is Eastman Chemical in Kingsport, Tenn. The largest manufacturer of PS is Hoechst Celanese of Frankfurt, Germany. There are a limited number of large manufacturers of PS in the world, one being in Japan and another in Denmark.
Although sorbic acid and its salts have been found to be effective against a long list of microorganisms that are responsible for food decay, its use as a rust preventative agent has not been previously recognized. There is currently no known published literature that discloses the use of PS for other than its widespread anti-microbial use, primarily in products directly or indirectly related to food, with some acknowledgement of its anti-microbial effect in unrelated food products, such as cleaning solutions primarily used for cleaning areas involving food, such as food preparation or processing areas.
Corrosion is a very serious problem in many industries. According to an article in McGraw Hill Encyclopedia of Science and Technology, xe2x80x9cThe cost of corrosion in the United States and other industrial countries has been estimated to be on the order of 4% of the gross national product.xe2x80x9d This estimated cost includes both the replacement cost and the cost of protecting against corrosion. Extensive efforts have been made in the design of products such as steam generators, heat exchangers, bridges, oil platforms and motor vehicles to minimize the destructive effects of corrosion. However, corrosion remains a problem in these traditional products. In addition to traditional products, new developments in the areas of energy sources, new materials and microprocessors present new challenges in the fight against corrosion. As new devices are developed on a submicrometer scale, even smaller amounts of corrosion will result in device failure.
For these reasons, a new method and product that is effective to prevent and guard against corrosion of metal is needed.
It is the object of the invention to provide an aqueous solution that will prevent rust. The aqueous solution of this invention includes PS in the form of powder or granules that have been dissolved in ordinary tap water or deionized water, at percentages above 0.3%. PS is at its optimum effectiveness as a rust preventive at pH 6.0 and above.
The formula for producing applicant""s PS solution rust inhibitor, in a concentrated form, is to mix at the following ratio 269.5 ml of water (49.9%), 0.5 ml of sodium nitrate (0.1%) and 270.0 ml of potassium sorbate (50.0%). This concentrated rust inhibitor will have a pH of about 10.2. One part of the concentrate should be diluted with 16 parts tap water or deionized water to produce applicant""s rust preventive water. This diluted rust preventive water will have about a pH of 6.5.
The PS dosages for rust and corrosion prevention differ from the dosages of PS that are used for the prevention of microbial degradation. PS concentrations are effective as anti-microbial food preservatives, generally in the range of 0.05% to 0.3%. Higher dosages are not used because of the bitter taste that is imparted by PS.
The low concentration of PS currently used in the food industry are not effective for preventing rust, corrosion and/or scale. Concentrations of PS above 0.3% in aqueous systems have been found to be increasingly effective against the rusting, corroding or scaling of metal with a fail-safe concentration of xc2x11.75% laboratory tested as consistently and indefinitely preventing rust, corrosion and/or scale.
Applicant has found that the PS solution of this invention has reduced conductivity and reduced oxygen content of tap water and believes that this is the technical explanation of how applicant""s PS solution functions to prevent rust. Furthermore, the combination of lower conductivity and reduced oxygen content renders the PS solution less viable for microbiological growth. This feature of applicant""s PS solution is responsible for eliminating rancidity in re-circulating water systems due to mold. Toxic biocides are often added to re-circulatory water systems to reduce and control microbiological growth. The elimination or reduction of biocides in re-circulatory water systems is an added enhancement of this invention. Furthermore, by substituting the PS solution for tap water in water-based products, such as paints, will also eliminate or reduce the addition of toxic biocides.